1. Field of the Invention
The invention relates to sighting devices for use on a tractor to enable a tractor driver to visually align the direction of movement of the tractor with previously cut swaths or furrows in a field, and particularly to sighting devices which are remotely adjustable by the driver while he is seated in the driver's seat of the tractor.
2. Description of the Prior Art
A variety of sighting devices have been utilized for attachment to tractors or farm implements towed by tractors to enable drivers seated in the driver's seats of the tractors to visually align the tractors with previously cut swaths or furrows dug into the ground by the towed farming implements. The sighting devices must be adjusted so that the tractors are oriented to pull the farming implements so that the farming implements cut swaths or furrows which are adjacent to and perfectly aligned with previously cut swaths or furrows when the sighting devices are in line with points in straight lines between the eyes of the drivers and edges of previously cut swaths or furrows. The state of the art for sighting devices, especially those for use in conjunction with tractors and farm implements, is believed to be accurately represented by U.S. Pat. Nos. 3,028,678; 2,827,704; 2,538,112; 2,559,761; 2,548,226; 3,932,028; and 4,034,480. None of the sighting devices disclosed in the above patents is adjustable by a person seated in the driver's seat of a tractor. Consequently, the sighting devices must be adjusted in a trial-and-error manner wherein the tractor driver dismounts from the driver's seat, adjusts the sighting device to an initial setting, remounts the tractor, and drives the tractor for a distance to see if the swath or furrow being cut by the towed farm implement is accurately aligned with the previously cut swath or furrow. Since it is very important that the swath or furrow cut by the towed implement be properly aligned with previously cut swaths or furrows, the above mentioned trial-and-error adjustment method may necessitate an unduly large number of trial settings before satisfactory adjustment of any of the prior sighting devices is achieved.
Accordingly, it is an object of the invention to provide a sighting device for use in conjunction with tractors towing agricultural implements, which sighting device avoids the necessity of the driver dismounting from the driver's seat in order to adjust the sighting device.
It is another object of the invention to provide a sighting device which avoids the necessity of a second person adjusting the sighting device in accordance with instructions from a driver seated in the driver's seat of the tractor.
Some of the previous sighting devices are attached to the farm implement being towed, rather than to the tractor. This approach to providing sighting devices requires a separate sighting device for each farm implement. Since the sighting devices are quite expensive, this approach is undesirable.
Accordingly, another object of the invention is to provide an adjustable sighting device which avoids the necessity of trial-and-error sighting methods which require dismounting of the tractor driver or assistance of a second person, which sighting devices are attached to a tractor rather than to a farm implement.
Another object of the invention is to provide a sighting device for attachment to a tractor, which sighting device is conveniently and continuously adjustable by a person seated in the driver's seat of the tractor.
Another object of the invention is to provide a low-cost sighting device which is adjustable from the driver's seat of the tractor.
Another object of the invention is to provide a sighting device in conjunction with tractors towing farm implements, which sighting device overcomes the shortcomings of the sighting devices of the prior art.
Another object of the invention is to provide a sighting device which is easily adjustable from the seat of a tractor and which maintains a correct sighting despite obrupt jolting of the tractor as it moves over irregular ground.